ELVTUNE(8)							   ELVTUNE(8)



NAME
       elvtune - I/O elevator tuner

SYNOPSIS
       elvtune	[  -r  r_lat  ]	 [  -w	w_lat  ]  [ -b b_max ] /dev/blkdev1 [
       /dev/blkdev2 ...	 ]

       elvtune -h

       elvtune -v

DESCRIPTION
       elvtune allows to tune the I/O elevator per blockdevice	queue  basis.
       The  tuning  can	 be safely done at runtime. Tuning the elevator means
       being able to change disk performance and interactiveness. In the out-
       put of elvtune the address of the queue tuned will be shown and it can
       be considered as a queue ID.  For example multiple partitions  in  the
       same  harddisk  will  share the same queue and so tuning one partition
       will be like tuning the whole HD.

OPTIONS
       -r r_lat
	      set the max latency that the I/O scheduler will provide on each
	      read.

       -w w_lat
	      set the max latency that the I/O scheduler will provide on each
	      write.

       -b b_max
	      max coalescing factor allowed on writes when  there  are	reads
	      pending in the queue.

       -h     help.

       -v     version.

NOTE
       Actually	 the  only fields tunable are those relative to the IO sched-
       uler. It's not possible to select a one-way or two-way elevator yet.

       For logical blockdevices like LVM the tuning has to  be	done  on  the
       physical	 devices.  Tuning the queue of the LVM logical device is use-
       less.

RETURN VALUE
       0 on success and 1 on failure.

HISTORY
       Ioctls for tuning elevator behaviour were added in Linux	 2.3.99-pre1.

AUTHORS
       Andrea Arcangeli  SuSE



Version 1.0			14 March 2000			   ELVTUNE(8)

UNIX/Linux commands referenced on this page:

1. at
2. as
3. factor